PURPOSE: To provide an automatic adjustment method for internal clock of each electric component gaining power from electric cable without necessity of new cabling for clock adjustment and without any additional work of a user.

CONSTITUTION: By exchanging clock information by way of electric cable 20 between a transmission component 10 having a transmission device 2 for transmitting clock information of an internal clock 1a via electric cable 20 and a reception component 11 (12) having a reception device 3a (3b) for receiving the clock information sent via the electric cable 20 and setting the time of internal clock 1b (1c), the internal clock 1b (1c) of the reception component 11 (12) is adjusted to the internal clock 1a of the transmission component 11.